Generally, in a printing work by a sheet-fed offset printing press, a sheet gripped and transported by a gripper supported by a travelling delivery chain is released from the gripping of the gripper after being printed and falls on a pile board to be piled. In such a discharging work, there are a method of discharging a large amount of sheets on one pile board and a method of piling a small amount of sheets on each of multiple pile boards. Moreover, the method of piling a small amount of sheets on each of multiple pile boards includes the following two methods. In one method, support pillars called corners are placed at four corners of a pile board on which sheets have been piled and another pile board is placed on the corners to stack the pile boards one on top of another. In another method, sheets are piled as follows. Endless chains are disposed at four corners outside a pile board in such a way as to travel in an up-down direction. A pile board is disposed to be supported by the four endless chains. The endless chains are made to travel to lower the pile board when a predetermined amount of sheets are piled on the pile board. Then, a new pile board is disposed to be supported above the pile board on which the sheets have been piled. Particularly, a discharging apparatus in which a small amount of sheets are piled on each of multiple pile boards by using endless chains is referred to as “circulating type” and description hereafter is given by using the circulating-type discharging apparatus as an example.
The circulating-type discharging apparatus is described in detail. The four endless chains disposed at the four corners outside the pile board travel synchronously with each other. In each of pairs of left and right endless chains as viewed in a direction in which the sheets are transported by grippers, multiple guide rails are attached to extend in a direction orthogonal to the sheet transporting direction, at equal intervals in a travelling direction of the pair of left and right endless chains, and a pile board called a delivery pile board is supported by a pair of front and rear guide rails in the direction in which the sheets are transported by grippers. In a circulating-type discharging apparatus configured as described above, when a predetermined amount of sheets are piled on a pile board supported by the pair of front and rear guide rail, the pile board is lowered by causing the four endless chains to synchronously travel. Then, the travelling of the endless chains is stopped when the guide rails above the guide rails supporting the pile board are set at predetermined positions. Another pile board is inserted into the pair of front and rear guide rails set at the predetermined positions from a lateral side of the discharging apparatus and the sheets are piled onto the new pile board. In other words, the operation of inserting the new pile board is repeated for each pitch of the guide rails and the sheets are thus piled in multiple stages (see Patent Document 1).
Moreover, such sheet discharging apparatuses include one in which, for example, three paper-sheet pile boards are arranged in a transporting direction of paper sheets. Specifically, first to third piles are provided and the first and second piles which are two piles on an upstream side in the transporting direction of the paper sheets are used for normal paper sheets. The normal paper sheets are alternately delivered onto the pile boards of these piles and piled in several stages. Meanwhile, the third pile on the most downstream side in the transporting direction of the paper sheets is used for sample paper sheets and waste paper sheets. The sample paper sheets and the waste paper sheets are delivered onto the pile board of the third pile and piled in fewer stages than those in the first pile and the second pile (see Patent Document 2).